1. Field
The invention is in the field of archery bows wherein the limbs of the bow are pivotally mounted on the handle or riser section of the bow and the principal energy stored in the bow is stored otherwise than through the bending of the limbs.
2. State of the Art
Most archery bows include a handle or riser section with a pair of limbs fixed thereto and extending from opposite ends thereof. A bowstring is coupled to the free ends of the limbs so that upon drawing the bowstring, the limbs are deformed, thereby storing energy in the limbs. Upon release of the bowstring, the deformed limbs forcefully return to their rest positions, releasing the stored energy to the bowstring and an arrow nocked thereon. Such bows are normally designed to have a certain draw length, draw weight, and, with compound bows, a certain let-off. Adjustment of the draw length and draw weight of the bow can usually be made within certain ranges by changing the length of the bowstring or the attachment of the limbs to the handle, or, with compound type archery bows, by also adjusting the length of the buss cables and the size or configuration of the eccentrics. Usually, such adjustment is difficult for the archer to perform himself and the range of adjustment is limited.
Various attempts have been made to increase the efficiency of a bow by pivoting the limbs of the bow to the riser section, making the limbs very stiff to minimize deformation, and providing some type of energy storage means, such as a spring, coupled to the bow limbs to store energy as the bow limbs pivot about their mounting to the riser as the bow is drawn. One such bow is shown in my U.S. Pat. No. 4,756,295 issued Jul. 12, 1988. With the bow shown in U.S. Pat. No. 4,756,295, I have discovered that not only can a very efficient bow be provided, but that the arrangement of the energy storage means and its coupling to the bow limbs allows production of a bow that is very easy for the archer to adjust over a very wide range of draw weights and let-offs, without substantially affecting other characteristics of the bow such as bow balance, weight distribution, and feel. Some adjustment of the draw length is also easily obtained, but with such bow, draw length adjustment usually requires changing one of the toggle links or the bow limbs, or both.
The bow of U.S. Pat. No. 4,756,295 includes a power cell or energy storage device coupled directly to one of the pivotally mounted bow limbs and means connecting the two bow limbs together so that they move in unison. The coupling of the power cell directly to one of the bow limbs generally requires that the power cell be located immediately adjacent the mounting of such limb, i.e. at one end of the riser section, usually at the lower end of such riser.
Most archery bows in use today are constructed so that the center of mass substantially coincides with the pivot point of the bow around the thumb when held in shooting position. This minimizes the torque on the bow during shooting of the bow and minimize the force the archer has to apply to counteract such torque and keep the bow level and steady during shooting. The placement of the power cell at the end of the riser as in the bow of my aforesaid patent undesireably limits the flexibility in design of the bow. Because the power cell is located at the end of the riser, the bow has to be designed about the power cell to ensure the proper balance. This usually means that the riser will be short, approximately eighteen inches for a preferred, balanced bow made according to the referenced patent. However, with a riser length of only eighteen inches, and with normal limb lengths, such a bow is shorter in overall length than most archery bows. This means that at a normal draw length of between twenty-eight and thirty inches, the angle of the string at the nocking point of the arrow, where the string is held by the archer, may be such as to pinch the archers fingers. Using a string release mechanism, many of which are commercially available, eliminates this problem, but in many cases it may be desireable to increase the length of the riser. If the power cell remains at the end of the riser, with a longer riser the mass of the power cell undesireably shifts the center of mass from the desired point and requires that the archer get use to and counteract the resultant torque during shooting.